Portable signs are particularly useful for advertising products and services outdoors, such as advertising gasoline prices or tire sales at service stations, or displaying menus in front of restaurants. Their special advantage is portability, but along with this advantage comes the disadvantage of the ease with which they can be toppled by gusts of wind. In the past, various spring mechanisms have been employed to allow the display frame to pivot to deflect the wind. U.S. Pat. No. 3,662,482 shows one such attempt in which a display frame is mounted onto a pair of massive coiled springs which support the weight of the display frame; these springs are mounted onto a base made from tubular steel members. U.S. Pat. No. 1,750,118 discloses another variety of spring mechanism. One form of this mechanism uses a series of tension springs to connect the bottom of the display frame to the leg. A second form of the sign uses torsion springs mounted on pivot bolts to bear on the sign.
Another spring mechanism is shown in Beck, U.S. Pat. No. 1,532,865, but this sign is designed to be permanently implanted in a road and yield to let cars pass over it. Its spring mechanism employs dual torsion springs, oppositely coiled and mounted between the mounting support and the display frame.